st: Mean Correction

Dear Statalisters,
In many papers authors appear to mean-correct variables prior to
estimation for certain reasons. Namely, they divide the respective
variables by their geometric means. However, in a panel data environment
this raises the question "Which geometric mean should I use?". Should I
divide my variables with a Country-specific geometric mean (using
"bysort country"); should I use Yearly-specific geometric mean (using
"bysort year"); or a pooled geometric mean for all years and countries?
Thank you.
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/